[PATCH v4 0/2] cpufreq: acpi-cpufreq: fix P-state index mismatch between perf->states[] and freq_table[]

[lirongqing]

From: Li RongQing <lirongqing@xxxxxxxxx>

perf->state is an index into perf->states[], but freq_table[] is built by
skipping duplicate _PSS entries, so the two arrays no longer share an index
space. Using perf->state to index freq_table[] therefore reads the wrong
slot. This series fixes the two remaining places that do so.

Changes since v3:
- Reword patch 1 and patch 2 per Zhongqiu Han's review: replace "duplicate
  frequencies" with "entries that are not lower in frequency than the previous
  one" to match the actual dedup condition; expand the extract_io() retry
  description to "sleeps through all 100 iterations - at least ~1 ms of
  usleep_range() plus 100 cross-CPU calls and I/O port reads, all with
  policy->rwsem held"; drop the trailing "through data->resume" from patch 2.
- Add Reviewed-by from Zhongqiu Han.

Changes since v2:
- Reword patch 1;
- Rewrite patch 2, using perf->state to index perf->states[] (its native
  index space) instead of the deduplicated freq_table[]
- Fix the Fixes: tags to point at the actual commits that introduced each

Changes since v1:
- Reword patch 1: v1 described it as an out-of-bounds read, which is wrong;
  it is an index-mismatch / wrong-result bug, not a memory-safety issue.
- Add patch 2 for get_cur_freq_on_cpu().
- Add Fixes: tags (not exact, but reasonable backport targets).

Li RongQing (2):
  cpufreq: acpi-cpufreq: fix P-state index mismatch in extract_io()
  cpufreq: acpi-cpufreq: fix P-state index mismatch in
    get_cur_freq_on_cpu()

 drivers/cpufreq/acpi-cpufreq.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

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2.9.4